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Coupled Aerosol-Cloud Systems over Northern Vietnam during 7-SEAS/BASELInE: A Radar and Modeling Perspective

Category: Optical/Radiative Properties and Remote Sensing

Volume: 16 | Issue: 11 | Pages: 2768-2785
DOI: 10.4209/aaqr.2015.11.0631
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Adrian M. Loftus 1,2, Si-Chee Tsay2, Peter Pantina2,3, Cuong Nguyen4,5, Philip M. Gabriel5,6, Xuan A. Nguyen7, Andrew M. Sayer2,8, Wei-Kuo Tao2, Toshi Matsui1,2

  • 1 University of Maryland, College Park, Maryland, USA
  • 2 NASA Goddard Space Flight Center, Greenbelt, Maryland, USA
  • 3 Science Systems and Applications Inc., Lanham, Maryland, USA
  • 4 National Research Council, Ottawa, Ontario, Canada
  • 5 Colorado State University, Fort Collins, Colorado, USA
  • 6 General Analytics L.L.C., Fort Collins, Colorado, USA
  • 7 Vietnam Academy of Science and Technology, Hanoi, Vietnam
  • 8 GESTAR/USRA, Columbia, Maryland, USA

Highlights

First-ever look at low-level stratocumulus over Vietnam by ground-based cloud radar.
Springtime stratocumulus (Sc) often coupled with biomass-burning aerosol layer.
Observations reveal diurnal cycle with frequent drizzle overnight.
Simulations reveal drizzle suppression in Sc over land with greater aerosol loading.
Reduced precipitation may compound poor air quality over region during spring.


Abstract

The 2013 7-SEAS/BASELInE campaign over northern Southeast Asia (SEA) provided, for the first time ever, comprehensive ground-based W-band radar measurements of the low-level stratocumulus (Sc) systems that often exist during the spring over northern Vietnam in the presence of biomass-burning aerosols. Although spatially limited, ground-based remote sensing observations are generally free of the surface contamination and signal attenuation effects that often hinder space-borne measurements of these low-level cloud systems. Such observations permit detailed measurements of structures and lifecycles of these clouds as part of a broader effort to study potential impacts of these coupled aerosol-cloud systems on local and regional weather and air quality. Introductory analyses of the W-band radar data show these Sc systems generally follow a diurnal cycle, with peak occurrences during the nighttime and early morning hours, often accompanied by light precipitation. Preliminary results from idealized simulations of Sc development over land based on the observations reveal the familiar response of increased numbers and smaller sizes of cloud droplets, along with suppressed drizzle formation, as aerosol concentrations increase. Slight reductions in simulated W-band reflectivity values also are seen with increasing aerosol concentrations and result primarily from decreased droplet sizes. As precipitation can play a large role in removing aerosol from the atmosphere, and thereby improving air quality locally, quantifying feedbacks between aerosols and cloud systems over this region are essential, particularly given the negative impacts of biomass burning on human health in SEA. Such an endeavor should involve improved modeling capabilities along with comprehensive measurements of time-dependent aerosol and cloud profiles.

Keywords

Aerosol-cloud interactions Radar observations 7-SEAS Cloud modeling


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